1. Field of the Invention
The present invention relates to apparatus for recording and reproducing video signals. More particularly, the invention relates to apparatus for reproducing recorded interleaved video fields as a field sequential video signal. (As discussed herein, "video" and "video signal" shall be taken to refer to the NTSC standard, although the invention is applicable as well to other video standards.)
2. Description Relative to the Prior Art
Conventional solid state imaging devices used in video cameras supply video information at the frame rate of 30 frames per second. Each frame is composed of two video fields apiece, each field occurring at the field rate of 60 fields per second. Such conventional solid state imaging devices produce a field sequential output by capturing the two fields (f.sub.1 and f.sub.2) of each frame in different successive sixtieths of a second.
While the above-described imaging devices produce satisfactory results when used in video cameras used to record motion pictures, problems occur when such devices are used to image still pictures, viz. in the event scene motion had occurred between successive fields of a still picture frame (as is likely), then the subsequent display of that still picture frame will appear less sharp. A loss in image quality occurs because a still video picture is produced by repeatedly displaying a single video frame on a video monitor, say by continuous reproduction of the recorded video frame from a magnetic recording disc. If the two fields of the displayed video frame are slightly different, the image will appear to have motion, or jitter, since the two fields may represent a moving subject in two different locations.
Efforts to overcome the aforedescribed image degradation have resulted in the use of full frame imaging devices capable of capturing both fields of the frame simultaneously. Copending patent application Ser. No. 596,890 discloses an apparatus employing a frame transfer type imaging device capable of simultaneous capture of both fields of a video frame.
The video signal produced from the disclosed apparatus is not field sequential, but instead is interleaved with lines from each of the two fields (i.e. one line from f.sub.1, then one line from f.sub.2, and so on). The interleaved fields must therefore be separated to produce a field sequential signal for, say, interlaced display on a video monitor. In an electronic still camera that utilizes a magnetic disc to store the video information, the separation of the interleaved fields could be accomplished prior to recording the video frame on the recording disc. This would require the use of a field store device to store one field while the other field was being recorded on the magnetic disc. Use of a field store would, however, increase the complexity and expense of the electronic camera.
The requirement for a field store could be eliminated if the interleaved video fields could be recorded directly on the magnetic disc and reproduced from the disc as a field sequential signal. The problem then, which is the basis of the present invention, is to provide an apparatus for reproducing recorded interleaved video fields as a field sequential video signal.